This invention relates to a plasma display panel and a method of forming a fluorescent screen of a plasma display panel.
There is generally known a DC (direct current) or an AC (alternating current) type plasma display panel or unit in which front and rear plates are arranged parallel to each other and a cell barrier constituting a plurality of display element cells is disposed between the front and rear plates.
The fluorescent screen or surface of the DC or AC type plasma display panel having the structure described above, is formed by the steps of coating a photosensitive slurry containing a phosphor to the rear surface of the front plate, exposing the coated surface by utilizing a photomask corresponding to the pattern of the fluorescent screen to be formed, and finally developing and calcinating the exposed surface.
Utilized as the photosensitive slurry is a mixture containing a phosphor, PVA(poly vinyl alcohol), or diazonium salt, for example, and a defoaming agent or surfactant may be added as occasion demands.
In the case when light is observed by the eyes of an operator after transmission through this formed fluorescent screen itself, the amount of the light is reduced during the passage through the fluorescent screen. For this reason, in the conventional technology, there has been developed a plasma display panel in which a fluorescent screen is formed on the wall surface of the cell barrier for increasing the luminance of the light, and the reflected light of the light emitted from the fluorescent screen is observed.
The plasma display panel of the type described above utilizes a spacer provided with holes each having a trapezoidal cross section as a cell barrier, and a slurry solution containing a phosphor is fed into the hole from a widened opening side thereof. The slurry solution containing a phosphor is coated on the wall surface of the spacer hole by sucking the slurry solution from the other side of the hole to thereby form the fluorescent screen on the spacer wall surface.
With the conventional fluorescent screen forming method of the character described above, it is necessary to coat and suck the slurry solution containing a phosphor to form the fluorescent screen on the wall surface of the spacer, and accordingly, the front plate and the rear plate are assembled with the spacer after the formation of the fluorescent screen on the wall surface of the spacer. This assembling working makes it difficult to precisely adjust the positions of the front and rear plates and the spacer, which requires high-precision work for the preparation of the spacer member. The spacer member is prepared by providing holes in a photosensitive glass material with hydrofluoric acid. However, in the present technique, it is difficult to provide a photosensitive glass having a size of more than about 30.times.30 cm.sup.2. Accordingly, it is not applicable to utilize the photosensitive glass to the large sized plasma display panels which are required for the recent industrial use. In addition, the recent plasma display panel mainly requires a discharging space having a thickness of about 100 to 200 .mu.m and hence it is difficult to assemble the spacer in such discharging space and handle such a thin glass.
Furthermore, the conventional DC or AC type plasma display panel has a structure in which the cell barrier is attached to either the front plate or the rear plate and a cathode (cathode and anode in the AC type plasma display panel) is formed on the rear plate so that it is impossible to apply the conventional fluorescent screen forming technique as it is.